Tyler D’Agostino

This meme rides a real TikTok/Instagram trend documented by Women's Health and National Geographic, but it oversimplifies the physiology. It's true that intense exercise acutely raises cortisol — that's normal and adaptive, not harmful: a literature review (Hayes 2015, cited in our own science base) shows this rise is transient and settles after the session, and that overtraining comes from a chronic load/recovery imbalance over weeks, never from a single session crossing some arbitrary intensity or duration threshold. An exercise physiologist quoted by National Geographic and an exercise researcher (Colenso-Semple) both confirm: sorting workouts into "good/bad cortisol" ignores that this rise is part of the very mechanism that makes exercise effective. The one real nuance: during a period of major life stress, poor sleep, or chronic underfueling, dialing down intensity can be reasonable — but that's not a general rule that "lower cortisol = better." Verdict: exaggerated — the meme binarizes a nuanced physiology that the science doesn't support for most healthy people.